The exchange of data plays an increasingly important role in business. Pertinent examples are bank transactions, stock exchange transactions and similar operations. The verification requirement has become more and more important. Questions such as “Where and when was a transaction ordered?”; “Where and when was the order received and executed?” have to be answered. To clear up such questions in connection with the verification requirement, the data to be transmitted during the transaction must be provided with supplementary information. This is currently done by signatures, manual entries of locations and persons or, for instance, by providing clocks in computers or supplementary information permanently entered in stationary computers. This becomes problematic in particular when the processing units transmitting transaction data are not stationary and are locally mobile or if they have reduced input possibilities for supplementary information.
Vehicle navigation systems are known which determine an individual instantaneous vehicle location on the basis of received signals from GPS (global positioning system) navigation satellites. The signals of the GPS satellites also include information about an instantaneous chronological time.
From PCT International Published Application No. 98 57125, for example, a vehicle navigation system is known which determines a vehicle's individual instantaneous position during driving and stores it together with time information. Time-dependent section information is generated and recorded in this manner.
Furthermore, a so-called FCD (floating car data) system has become known in which locations of vehicles of a vehicle fleet are determined together with additional parameters such as vehicle speed, for instance, and transmitted via a radio link to a central station where the received vehicle data are analyzed in order to derive information about obstructions of traffic on particular sections of the road network, for example.